In general, belt drive systems in which a belt is wrapped around a plurality of flange pulleys each having a pulley groove on its outer circumferential surface include a tension applying means, such as an auto tensioner, which applies predetermined tension to the belt looped over all of the pulleys.
To avoid the provision of such a tension applying means, a belt attachment jig has been suggested which is configured to extend a belt in a circumferential direction in attaching the belt to a plurality of pulleys, and allow the belt to pass over the flange of a pulley, thereby attaching the belt to the pulley.
In the case, for example, where the belt is wrapped around two pulleys, the belt attachment jig is used in such a manner that the belt is looped over one of the two pulleys (a first pulley), and in this state, the belt attachment jig is attached to a second pulley. In this attachment state, the belt is wound around the belt attachment jig, and a belt portion located on the rear side of the belt attachment jig in a pulley rotational direction is fitted to the pulley groove of the second pulley, and a belt portion located on the forward side of the belt attachment jig in the pulley rotational direction is pulled laterally toward a near side of the second pulley. Accordingly, the belt attachment jig is sandwiched between the belt and the pulley groove. The phrase “near side” as used in this specification refers to the side closer to an operator who is attaching the belt, and the phrase “back side” refers to the side opposite to the side closer to the operator.
The belt attachment jig in this attachment state is moved forward in the pulley rotational direction by rotating the center bolt of the jig-attached pulley with a wrench, etc., to gradually increase the area of the belt which is fitted to the pulley groove, and make the belt completely wrapped around the jig-attached pulley in the end.
When the belt is wrapped around the pulleys in such a manner as described above, the belt wound around the belt attachment jig passes through a lateral side of the near side of the jig-attached pulley and is led to the first pulley. Thus, if the belt is wrapped around the pulleys by rotating the second pulley, the belt entering to the first pulley may be pulled hard laterally toward the near side of the first pulley due to the tension generated by the wrapping of the belt. This may result in the detachment of the belt from the first pulley. To avoid the detachment of the belt, belt detachment preventing jigs for preventing detachment of the belt have been known.
For example, Patent Document 1 discloses a belt detachment preventing jig including a plate-like detachment preventing member located on a rim side of a pulley flange, an engagement groove formed in the bottom of the detachment preventing member, and a sandwiching portion which protrudes from the bottom of the detachment preventing member so as to extend along the inner surface of a pulley groove, wherein the pulley flange is sandwiched in the engagement groove, and the sandwiching portion is fixed to the jig by being sandwiched between the belt and the pulley groove. Therefore, even if the belt is pulled toward the near side of the pulley, the detachment preventing member prevents the detachment of the belt from the pulley.